Glass drill



April 29, 1952 w c, PALMER 2,594,487

GLASS DRILL Filed Sept. 3, 1947 ilnnentur M45012 6' PALMER m 5 Slum-nay Patented Apr. 29, 1952 GLASS DRILL Wilbur C. Palmer, Corning, N. Y., .assignor .to

Corning Glass Works, flaming,.N. Y.,1a..corpra 'tion of NewYork Applicationfieptembcr 3, 1947, Serial No. 771,927

'5 Claims. (Cl.?255--161) The present invention relates to drilling apparatus especially suitable for use in drilling holes in thick glass or other thick bodies of ceramic materials and the like, and is particularly concerned with apparatus suitable for drilling holes of diameter and larger.

It has been common practice for some time past to drill holes of /8" to /2 in diameter by the use of suitably lubricated bits comprising sticks of tungsten carbide triangular in crosssection and having working faces of pyramidal form bounded by three triangular outlines, with the common apex of these outlines being coextensive with a line drawn lengthwise through the center of the stick.

In the drilling of holes larger than /2" in diameter it has been the usual practice to resort to the'use of a conventional form of tubular bit,

to the end of which a suitable grinding compound is added from time to time during the grinding process. This latter form of drill is open to seV- eral objections: It is very slow; there is considerable danger of objectionably scratching the glass surface with the abrasive; and since the abrasive acts on the outer surface of the tool as well as on the glass, the tool diameter becomes smaller as grinding continues, so that the hole diameter tends to objectionably taper. To prevent chipping of the border of the perforation, it is common practice to drill part way through the body and then reverse it and drill through from the opposite side. Since the tubular form of drill has no pilot, it becomes very difiicult to drill the hole about the same axial center from both sides.

One object of the present invention is a glass drill free of objections found in the use of a tubular form of drill.

Another object is a new form of glass drill adapted to drill accurately-formed holes through heavy glass bodies without the necessity of the use of an abrasive material.

A still further object is a novel form of drill composed of a cluster of drill bits adapted to drill through heavy bodies of glass in a fraction of the time required when using conventional forms of tubular bits.

A further object is a drill assembly adapted for drilling relatively large holes and having a leader or pilot bit enabling perfect alignment of holles in part drilled from opposite sides of a glass b0 y.

Other and further objects of the present in vention will be apparent from the following dcscription and claims, and will be understood by reference to the accompanying drawing which, by

'2 way of illustration, shows a preferred embodiment of the invention.

In the accompanying drawing Fig. 1 is a plan view of the working end of a drill assembly embodying the invention.

Fig. 2 is a perspective view ofthe assembly.

Fig. 3 is a side elevational view of the assembly as seen when looking in the direction indicated by arrows 3-3 in Fig. 1.

Referring to the drawing in detail, the drill assembly comprises a cluster of three drill bits I I,

I2, and I3, assembled about a similar drill bit I I, and clamped in a chuck I5 by suitable set screws. such as screws I6.

Each of the drill bits II, I2, and I3 are alike. and accordingly a description of one will suflice for all. The drill bit II comprises a stick of tungsten carbide triangular in cross-section and having a working face of pyramidal form comprising three triangular surface areas 2I, 22, and 23, respectively, with a common apex 24.

The drill bit It is identical to bit I I except that it is, sufficiently longer that when assembled in chuck I5, the base 26 of its working surface is back of apex 24 of bit I I and of the apexes of bits I2 and I3; whereas, the apex or point 25 of bit I4 is well forward of bits I I, I2, and I3, bit I4 thus serving as a leader or pilot bit for the drill assembly.

The chuck I5 has a closed bottom I! with a projecting drill shank I8 so located that it is coaxial with the drill bit I4.

In the use of the drill assembly, initially all of the drilling is done by the pilot or leader bit I4, but slightly before the depth of cut is such that the base 26 of the bit face encounters the material, the apex 24 of bit II, and the apexes of the other drill bits I2 and I3, engage the material. As drilling proceeds, edge 21, forming the line of juncture of the working faces 2| and 22 of drill bit II and the corresponding edges of drill bits I2 and I3, engage the work to progressively increase the hole diameter to that represented by a circle drawn about the working edge 28 of the bit II and about the corresponding edges of the other two bits I2 and I3. As soon as drill point 25 passes through the work, the work may be reversed and drilling started from the other side with positive assurance that the final hole produced will be accurately formed and of uniform dialmeter throughout the thickness of the materia What is claimed is:

l. A drill comprising a leader drill bit of triangular configuration in cross-section and a 3 cluster of at least three similar drill bits arranged symmetrically about and in abutting relation with said leader bit.

2. A drill such as defined by claim 1 wherein the working ends of all the bits are substantially alike in size and cross-sectional configuration.

3. A drill comprising a leader drill bit and a cluster of three similar drill bits arranged symmetrically about said leaderbit, and wherein each bit is of triangular configuration in crosssection, and each bit of the cluster is arranged with one of its fiat sides abutting a flat side of the leader bit.

4. A drill such as defined by claim 3 wherein each of the bits has a pyramidal working face comprising three triangular flats having a common apex falling on a line running lengthwise through the center thereof.

5. A drill such as defined by claim 4 wherein the apexes of the triangles comprising the work- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 51,925 Coles Jan. 9, 1866 134,805 Hipkins Jan. 14, 1873 1,666,898 Hanson Apr. 24, 1928 2,174,389 Poletis Sept. 26, 1939 2,245,995 Merry June 17, 1941 2,337,322 Gascoigne Dec. 21, 1943 

